In the 19th century the Rhineland was first cartographed using triangulation. First from the French, then continued by the Prussians. With triangulation one divides an area into connected triangles and determines the relative position of the corners (topographic points or benchmarks) through measurements of the angles between them with a theodolite.

But then you still don't know the size of the triangles. For that you need the length of one side of a triangle. In a first order triangulation network the corners are about 30 to 50 km apart. With the technology of the 19th century it was impossible to do precise measurements of such distances.

Therefore only a rather small distance of a few kilometers was measured with iron rods - a so called basis - and transfered via some intermediate benchmarks to one of the triangles sides. For the Rhineland triangulation network this is the basis Bonn, which was chosen for it's flat and straight terrain along the road between Bonn and Cologne and its vicinity to the observatory at the university of Bonn. 1847 the distance of a good 2 km was measured to one millimeters precision.

Required equipment: A tape measure or folding rule. You don't have to measure to a millimeters precision, just round to the nearest integer value.

The stages are along a road - you best use a bicycle or your car to reach them, parking lots are mentioned as additional waypoints. But you can also walk the distance of about 5 km total. Public transport: take tram line 16 and stop at Buschdorf.

Punkt A: N50° 45.807' E007° 03.318'
On the replica of the measurement postament is a map of the basis Bonn. A = distance between point ("Punkt") A and point C in centimeters. Use the tape measure, not the info from the text!

Nearby is a height benchmark numbered 30. B = distance height benchmark to front left leg of the postament in meters.

Punkt B: N50° 45.428' E007° 03.957'
From the point you see a three-digit number on a pole. C = number on pole.

Punkt C: N50° 45.025' E007° 04.646'
D = distance from the edge of the manhole cover of point C to the front left leg of the postament replica in meters.

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